if not a:
print("List is empty")
Using the implicit booleanness of the empty list is quite Pythonic.
GeeksforGeeks
geeksforgeeks.org › python › python-check-if-list-empty-not
Check if a list is empty or not in Python - GeeksforGeeks
October 24, 2024 - In article we will explore the different ways to check if a list is empty with simple examples. The simplest way to check if a list is empty is by using Python's not operator.
Top answer 1 of 16
7312
if not a:
print("List is empty")
Using the implicit booleanness of the empty list is quite Pythonic.
2 of 16
1556
The Pythonic way to do it is from the PEP 8 style guide.
For sequences, (strings, lists, tuples), use the fact that empty sequences are false:
# Correct: if not seq: if seq: # Wrong: if len(seq): if not len(seq):
Top answer 1 of 2
25
The empty list, [], is not equal to None.
However, it can evaluate to False--that is to say, its "truthiness" value is False. (See the sources in the comments left on the OP.)
Because of this,
Copy>>> [] == False
False
>>> if []:
... print "true!"
... else:
... print "false!"
false!
2 of 2
4
None is the sole instance of the NoneType and is usually used to signify absence of value. What happens in your example is that the empty list, taken in boolean context, evaluates to False, the condition fails, so the else branch gets executed. The interpreter does something along the lines of:
Copy>>> a if a else None
[] if [] else None
[] if False else None
None
Here is another useful discussion regarding None: not None test in Python
Flexiple
flexiple.com › python › check-if-list-is-empty-python
Python isEmpty() equivalent – How to Check if a List is Empty in Python - Flexiple - Flexiple
Check if a list is empty in Python by using the len() function or compare the list directly to an empty list.
TutorialsPoint
tutorialspoint.com › How-to-check-if-a-list-is-empty-in-Python
How to check if a list is empty in Python?
In the example below, we are going ... list is empty or not by using an if condition and the not operator. If the list is empty, then it returns True; otherwise, False, which means the list is not empty....
Built In
builtin.com › articles › python-check-if-list-is-empty
Python Check if a List Is Empty: A Guide | Built In
The most common way to test if a list is empty in Python is to use the truth value testing method with the not operator. The len() function is best if you are working with different data structures, while the == operator makes your code easier ...
freeCodeCamp
freecodecamp.org › news › how-to-check-if-a-list-is-empty-in-python
Python isEmpty() equivalent – How to Check if a List is Empty in Python
April 19, 2023 - In the code above, we used an if statement and the not operator to check if the people_list was empty. You can use the len() function in Python to return the number of elements in a data structure.
Reddit
reddit.com › r/learnpython › should i return none for an empty data array?
Should I return None for an empty data array? : r/learnpython
June 23, 2024 - Subreddit for posting questions and asking for general advice about all topics related to learning python. ... Sorry, this post was deleted by the person who originally posted it. Share ... Agreed. This is a special case of the Null Object Pattern. It simplifies what callers need to be prepared to handle. For example, if a caller wants to iterate over all elements, they don't have to check for None first, they can just iterate over the empty list.
Curict
en.curict.com › item › 9a › 9a5983d.html
Checking if a Python list is empty
There are several ways to check if a list contains any elements, such as using “if not”, the built-in len function, or comparing it to an empty array. In Python, an empty sequence (an empty list) is considered False, so you can use the if not operator to check if a list is empty.
Python.org
discuss.python.org › ideas
Allow None in list initializer to return an empty list: list(None) -> [] - Ideas - Discussions on Python.org
November 21, 2024 - To avoid boiler plate code: def prepend_42(elements: Iterable[int] | None = None) -> list[int]: if elements is None: return [42] return [42] + list(elements) would be equivalent to def prepend_42(elements: Iterable[int] | None = None) -> list[int]: return [42] + list(elements) # Wanted behavior # prepend_42() -> [42] # prepend_42([100]) -> [42, 100]
iO Flood
ioflood.com › blog › python-check-if-list-is-empty
Learn Python: How To Check If a List Is Empty?
June 27, 2024 - The if statement first checks if my_list is None, and if it’s not, it checks if my_list is empty. If either condition is True, it prints ‘Variable is None or list is empty’. While using the not operator is a common approach, Python offers other ways to check if a list is empty.
Python Morsels
pythonmorsels.com › checking-for-an-empty-list-in-python
Checking for an empty list in Python - Python Morsels
August 20, 2024 - One way to check whether a list is empty is to check the length of that list. If the length is 0, the list must be empty: >>> numbers = [] >>> if len(numbers) == 0: ... print("The list is empty.") ... The list is empty.
Codedamn
codedamn.com › news › python
Python List Is Empty: All Methods to Check
July 1, 2023 - A: No, Python does not have a built-in function specifically to check if a list is empty. However, you can use Python's built-in len() function or simply use the list in a boolean context to check if it's empty.
Stack Abuse
stackabuse.com › how-to-check-if-list-is-empty-in-python
How to Check if List is Empty in Python
February 20, 2023 - This is basically a manually implemented truth value test. So if the list is not empty the function will return True and if block will be executed. This approach is less common as we can achieve the desired results even without using bool(), but it's not a bad thing to know how Python works ...
datagy
datagy.io › home › python posts › how to check if a python list is empty
How to Check if a Python List is Empty • datagy
August 26, 2022 - What is the best way to check if a Python list is empty? The best way, according to PEP-8, is to use the if keyword. By writing if a_list:, you can evaluate whether a list is empty or not, since an empty list will return False.
Enterprise DNA
blog.enterprisedna.co › python-check-if-list-is-empty-7-methods-explained
Python: Check If List is Empty (7 Methods Explained) – Master Data Skills + AI
There isn’t a specific built-in function to check for empty lists in Python. However, you can use the implicit boolean value of a list or the len() function to achieve this.
Programiz
programiz.com › python-programming › examples › check-empty-list
Python Program to Check If a List is Empty
It is the most pythonic way of testing emptiness. If you want to learn more about boolean truth value, you can refer to Truth Value Testing. my_list = [] if not len(my_list): print("the list is empty")
Vultr
docs.vultr.com › python › examples › check-if-a-list-is-empty
Python Program to Check If a List is Empty | Vultr Docs
December 6, 2024 - The len(my_list) == 0 condition will be True if my_list is empty, triggering the print statement.
Sentry
sentry.io › sentry answers › python › check if a list is empty in python
Check if a list is empty in Python | Sentry
The Python style guide, PEP-8, recommends checking whether a list (or other sequence) is False to determine that it is empty.
Designcise
designcise.com › web › tutorial › is-an-empty-list-in-python-none
Is an Empty List in Python "None"? - Designcise
November 10, 2023 - Although, in a boolean context, ... == None) # False · In Python, None is a special constant that indicates the absence of a value, while an empty list represents a list with no elements....